The inner diameter of the tube rings is 105 mm for Telescopes between 50 to 103mm tube diameter can be mounted adjustable The adjustment crews have teflon inlays for avoiding unaesthetic scratches and pressure marks on the telescope while still ensuring reliable clamping Solid metal finder-guide scope rings for compact telescopes and finders with flat support surface and knurled metal screws There is a female M6 thread at the base for easy adaption to dovetail bars or dovetail clamps; big screws with maximum grip allow easy use - even with gloves Set: pair of two tube rings made of metal; the Astromania finder-guide scope rings are suitable for small and medium-sized guiding telescopes; ideal for astrophotography for mounting a finder-guide scope parallel to the main telescope Astromania adjustable tube rings for astrophotography.Set of 2 finder-guide scope rings for finder-guide scopes between 50mm and 103 mm tube diameter. The finder-guide scope rings from Astromania Optics allow a reliable and above all stable adaption of telescopes parallel to the main instrument. Most common use is astrophotography. With the knurled thumb screws, the finder-guide scope is adjustable and you can centre a sufficiently bright star in the eyepiece or the the autoguider. And the tube rings are suitable for bigger finder scopes, too. The adaption of the tube rings to the telescope. There is a female M6 thread at the base for easy adaption to dovetail bars or dovetail clamps. Big screws with maximum grip allow easy use - even with gloves.